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1610s, from French flagrance or directly from Latin flagrantia, noun of quality from flagrantem (see flagrant).
c.1500, "resplendent," from Latin flagrantem (nominative flagrans) "burning, blazing, glowing," figuratively "glowing with passion, eager, vehement," present participle of flagrare "to burn, blaze, glow" from Latin root *flag-, corresponding to PIE *bhleg- "to shine, flash, burn" (cf. Greek phlegein "to burn, scorch," Latin fulgere "to shine"), from root *bhel- (1) "to shine, flash, burn" (see bleach (v.)). Sense of "glaringly offensive" first recorded 1706, probably from common legalese phrase in flagrante delicto "red-handed," literally "with the crime still blazing." Related: Flagrantly.